Fluid pressure motor of the expansible chamber type with piston operated snap action valve



May 27, 1947. w. H. DE L ANcEY FLUID PRESSURE MOTOR OF THE EXPANSIBLE CHAMBER TYPE WITH PISTON OPERATED SNAP ACTION VALVE Sheets-Sheet 1 Filed OGt. 30, 1944 2 @w Ky@ Y' V115: sv 1,2.' f i ..45

A' Ff .if MZ y INVENTOR, Vanta /lafz BY )had ATTORNEYS May 27,1947. w. H.' DE LANCEY 2.421.318

FLUID PRESSURE MOTOR OF THE EXPANSIBLE CHAMBER TYPE WITH PISTON OPERATED SNAP ACTION VALVE' INNEN-ron,

d #2M ATToRNEYs UNITED STATES. PATENTA ol-'rlcs FLUID PRESSURE MOTOR OF THE EXPANSI- BLE CHAMBER TYPE WITH PISTON OP- ERATED SNAP ACTION VALVE Warren H. De Lancey, Sprlngiield, Mau., assignor to Gilbert t Barker Manufacturing Company, West Springiield, Mass., a corporation ot Massachusetts Appllcatlon October 30, 1944, Serial No. 560,924V

Claims. (Cl. 121-164) e l 2 This invention relates to improvements in movide an improved mounting for the pressure uid tors of the reciprocating-piston type adapted to conduits which lead from one cylinder head to be actuated by iluid under pressure. s the other for conducting pressure Iluid to the The invention has for one object to provide in valve mechanism and/or conducting pressure a motor of the class described, avalve mechanism 5 fluid to or discharging it from that end oi' the including a slide valve and means including toggle, motor cylinder opposite to the end where the valve links and springs, for moving the valve with a mechanism is located. e snap action from one to the other of its two ex 'A further object of the invention is to provide treme positions, together with a valve actuator, an improved'housing for the motor cylinder, said movable by the piston of the motor and adapted conduits and valve mechanism. to move the toggle links from either extreme po. `A further object of the invention is to provide sition to and across mid position-the springs then in a motor of the class described, valve mechacompleting the movement of the links and the n ism oiY generally simplied and improvedmeactuator characterized in that said actuator chanical structure. can be positively moved by the motor piston A further object of the invention is to provide throughout its entire stroke if and when said in a motor of the class described. generally simsprings and toggle links fail for any reason to plitled and improved mechanical structure.

move the actuator. The invention will be disclosed with reference 'I'he invention has for another object the proto the accompany drawings. in Whichvision in a motor of the class described, of im- Fig. 1 is a small-scale exterior elevational view proved valve mechanism including a reciprocable showing the motor of this invention mounted on a valve actuator, movable by the motor piston from wheeled cabinet containing e crease drum and either extreme position to and slightly beyond adapted t0 aetuete agresse pump for dispensing mid position and movable the balance of the way grease from the drum; A

by springs associated with toggle links and act- 2 Fig- 2 seplen View 0I the meter;

ing on opposite sides of the actuator, and fulcrum Figs. 3 and 4 are sectional elevational views means for said means bodily movable laterally taken on the lines 3 3 and 4 4, respectivelyof of the line of movement of the actuator to auto# Fig. 2; and

matically equalize the pressure on opposite sides Figs. 5, 6 and 7 are fragmentary sectional views of the actuator. 3i taken on the lines 5 5, 6 8, and 1 1, respec- The invention has for another object to provide `tively 0! F18. 2i f in a motor of the class described, valve mecha Fig. 8 is a fragmentary Seetionel View 1111iS- nism for controlling the supply of pressure iluid twelve of the mounting of the air-conducting to said cylinder and including a slide valve and tubes: and a spring-pressed pressure plate for holding the Fig. 9 is a. fragmentary sectional elevational valve against its seat, and passages and recesses view illustrative of an operating connection bein said valve and pressure platefor enabling the tween the rod of the valve actuator and the p18 pressureluid to act equally and in opposite dit0n 1'0drections on both the valveI and the pressure plate, l Referring t0 these dl'eWingS; the grease pump whereby the valve is held to its seat solely by 4o and its actuating motor are shown in Fis. 1 as the pressure of the pressure-plate spring unanect- Supported from the top wall l of a wheeled eabed by variations in the pressure of the actuating inet 2. adapted to contain a grease drum l, the fluid, cover of which has been removed. The arrange- The invention has for another object to proment iS Such that the grease pump is located in vide in a motor of the class described an improved drum 3, near the bottom thereof and submerged mounting and arrangement of parts. whereby the in the grease, while the motor is exposed outside valve mechanism is located entirely on one head the cebinetand encased in a cap which cooperates with said The grease pump (Fig- 3) consists 0f e cylinone head to form a housing. der 4 within a barrel B, having threaded on its The invention has for a further object to proso, lower end a casing 1. containing afoot valve 8.

. 3 cooperating with a seat in the casing. Slidable in cylinder 4 is a piston including a plurality of packing rings 3 of substantially V-shape cross sectional form, mounted in a stack on a portion 9 of a piston rod I0. Aspreader ring Il, slidably mounted on the portion 3 engages the uppermost ring 8 and a nut l2, threaded on the lower `end of the piston rod has a groove to engage and at the lower ring s. Nut i2 eiamps the rings between it and the spreader and the latter against a shoulder onthe piston rod. The piston rod has a diametrical hole i3 therethrough, located'above the piston, and an axial passage I4 extending from hole I3 downwardly to the lower end of the piston rod and` communicating with an axial passage I5 in a nut |2. The lower end of the latter is threaded into the upper end o! a hollow cylindrical valve cage IB, having in its lower end a seat with which a ball valve Il is engaged. A spring I8 acting between valve I1 and a seat I9 on the extreme lower end oi nut I2 tends to hold valve I1 on its seat. The seat I9 has a hole extending diametrically therethrough and communicating with the lower end of passage I5.

The upper end of the barrel 5 is threaded into an adapter 2| and the latter is threaded into a central opening in the lower wall of the base 22 `ci the air motor which base rests upon the wall The piston rod extends through this base and through a stuillng box mounted in the base and including a stack of packing rings 23 of substantially V-shaped cross section, a gland 24 and a spring 25, which acts against a seat in adapter 2| and presses .the gland 24 upwardly to compress the packing rings 23. The gland 24 has in its external periphery and intermediate its ends a circumferential groove 26 which is connected by one or more radial passages 2 to a counterbore 28 in the gland. This counterb'ore provides an annular passage communicating through an annular passage 29 in the adapter with the upper end of the grease pump cylinder 4. A grease outlet passage 30 is provided in base 22 having one endin communication with groove 2B and the other threaded to receive the usual greasedispensing hose (not shown) The operation of the ygrease pump is the usual one. On an upstroke of the grease piston, valve |1 is closed and a suction is created in the lower end of cylinder 4, raising foot valve 3 and allowing grease to enter the cylinder 4 below the piston. On a downstroke of the piston, valve 3 closes and valve I1 opens, allowing grease to pass through the piston to the upper side thereof, to be lifted on a succeeding upstroke of the piston and expelled by way of passages 23, 23, 21, 26 and 30 to the dispensing hose with its usual valve controlled nozzle (not shown).

The iluid pressure, such as compressed air for example. which is used for actuating the air motor enters a cylinder 3| formed in base 22 at a point diametrically opposite from the grease outlet passage 30. The outer end of cylinder 3| is closed by a nut 32, except for an axial passage 32' therein which communicates with the pressure iluid supply pipe 33, xed to said nut. The in' .r end of cylinder 3| is bored out and threaded to receive a valve seat member 34, the opening in which is connected by a` passage 35 to the groove 23. A valve 33 cooperates with the seat to open or closethe passage 35, accordingly as the supply of pressure iluid to cylinder 3| is turned oi! or on, respectively. A piston 31, slidable in cylinder 3|, is fixed to valve 36 and is movable by the pressure iluid to close the valve. A spring 33. acting between the valve seat member 34 and piston 31 acts to open the valve, when the pressure iluid is not available at the requisite pressure in cylinder 3|. The inner end of nut 32 forms a stop 33 to limit the "outward movement of the piston 31 and is turned down to provide an annular space between it andthe cylinder. In the inner end oi.' this stop 33 are crossing diametrica'l slots 40 which ailord communication between air inlet passage 32' and said annular space when the piston engages the stop. A radial outlet passage 42 is provided through the peripheral wall of the cylinder 3| near its inner end and opening through the bottom wail oi base 22 in overlying relation with the open upper end` oi grease drum 3. Whenever the air supply to the actuating motor is shut oil, the grease outlet, and particularly the dispensing hose, is automatically vented through passage 42-any grease expelled falling into drum 3.

The base 22 has on its lower face a plurality of radial ribs 4| to enter the opening in the wall I-the shoulders formed at the outer ends of these ribs engaging the wall of such opening and lserving to properly center the grease pump relatively thereto. The base is held in place by a plurality of cap screws 42' which pass through wall and thread into the base.

The top of base 22 has an annular wall 43 having finished internal and external cylindrical surfaces. A cylinder head 44 has an annular wall 45 with finished internal and external surfaces of the same diameter as the respective internal and external surfaces on the head-forming top portion of base 22. A shell 46, such as a length of metal tubing. fits into the confronting cylindrical recesses in the opposed heads 22 and 44, engaging the internal peripheral walls of each and having its ends resting against gaskets 46'. A plurality of tie bolts 41, pass throughwall 45 of head 44 and thread into holes in wall- 43 of head 22, thereby clamping the ends of the shell against the gaskets 48 and the latter against the upper and lower cylinder hea-ds. The cylinder of the air motor, formed within shell 43 and heads 22 and 44 is designated 48.

. The external peripheral surfaces of walls 43 and 45 engage the internal peripheral wall of a shell 49, which is made of metal tubing and which at its lower end seats on base 22. Thev upper end of shell 49 extends above the head 44 and is closed by a pressed metal cap 50, held in place by screws 5I as will later appear. The upper portion oi' shell 49 and its cap 53 serve to enclose all of the valve mechanism which is mounted on top of the upper head 44. The annular space 52 between the shells 46 and 43 is connected to the enclosed space -above head 44 by a hole 53 (Fig. 2) in such head and is used as an exhaust passage. This passage is 'conneoted to the atmosphere by a large notch 54 in the external periphery of wall 43 (Fig. 3).

The upper cylinder head 44 has upstanding therefrom a bracket 5E (Figs. 2 and 6) which has in one vertical face thereof a cylindrical recess to receive a cylindrical valve seat member 33 made of suitable hard material, such for example as Nitralloy." This seat is clamped to the support with a gasket 58' therebetween by three cap screws 31 passing horizontally through the brackmanera y The passage 84 at its l later appear. The upper end of passage S (Fig.

4) communicates with th'e outer end of a horizontal passage tl in web tt' and the inner end of passage tl communicates with one end of a passage tt. the other end of which communicates with the central passage 58 in the valve seat as shown in Fig. 6. The passage 6E at its lower end communicates with the upper end of cylinder 08 and its upper end communicates with a passage tt leading te the upper passage t0 in the valve seat.A The passage tt (Fig. lil)Y at its lower end communicates with' the lower end of cylinder te, as will later be described in detail. The upper end of passage tt communicates with the outer end of a horizontal passage l0', formed in web t5' and,

the inner end of passage 'it is connected to a passage 'il leading to thelower passagett in the valve seat. as shown in Fig. 6.

The air supply passage @d (Fig. 4) is connected by a tube l2 to a passage 13 in base 22 and such passage opens intothe outer end of cylinder tl 1- to which the compressed air vsupply pipe 33 is connected as already described. lThe passage 00 is connected by a similar tube lll to a short vertical passage lt in the" base 22. From the lower end of passage l5. a passage it extends in up` 6 and in communication with one oi two slots 00 in "opposite side faces of yoke 8l, whereby the upper end of the motor cylinder 48 can exhaust into the space within cap 00 and by the passages 03, B2 and B0 to the atmosphere. When the valve is in the second position, the upper passage 60 is wholly uncovered by, and lies beyond the outer periphery of. the valve, whereby th'e lower end of the cylinder d8 is connected in a similar manner to exhaust l to the atmosphere.

The valve guide member 8 3 (Figs. 2 and 6) has. a cylindrical recess opening into the yokereceiving slot therein. In this recess is mounted a pressure plate 01 the diameter of which is lust slightly less than the width of the yoke 8l. A spring t@ encompassing a hollow hub t0 on the pressure plate and acting against the end'wall g of the recess in the valve guide et forces the valve ward-ly diverging relation. opening into the lower end oi cylinder tt. Each tube has its ends engaged in confronting recesses in the two cylinder heads. Each lend of each tube has thereon a suitable packing ring. such as .the O-ring 'i8' of rubber, or the like, herein shown. Such ring (Fig. 8)..is forced over the tapered extremity of the tube and into a circumferential groove in th'e tube. The O-ring it is compressed between the tube and the peripheral wall of the tube-receiving recess and providesan air tight Joint. The ends of each tube do not necessarily have to be clamped against the end walls of the two confronting tubethese recesses.

The valve 11 (Figs.l 6 and 7) is mounted in an elongated slot 80 in a yoke 0i with freedom to slide as well as turn therein. The ends of slot Il are semi-cylindrical and of substantially the same radius as the'valve. Th'e yoke 8l may be a die casting and its actuatingy rod 02 may be fixed thereto during the die casting operation.

The yoke is vertically slidable in a slot formed in the inner face of a guide member 83 which is fastened by cap screws 84 (Fig. 5) to the bracket Il and is located with close accuracy relatively thereto by dowel pins 85. The valve yoke is adapted to move valve 11 from a position in which one of its end recesses 18 will interconnect the upper and central passages 59 and 08, respectively, to a position in which the same recess interconnects th'e central and lower passages 08 and 00, respectively. When the valve is in the first position, the lower passage 00 is wholly uncoveredby and lies beyond the outer periphery of. the valve This pressure plate has an axial opening therethrough'. A stud 0l fixed to the end wall of said recess in the guide member-t3 extends into the hollow hub 89 andcarries a suitable packing, such as an O-ring 02 of rubber or the like to pre'- vent leakage from the hub.

The axial passage 19 in valve il allows pressure fluid to pass from one recess 'it to the other and thus balance the pressures acting on opposite sides of the valve. So also, the hole t@ in the pressure plate allows the pressure fluid to pass into the hollow hub and enable the pressures acting on opposite sides of this plate to be approximately balanced. In this way, substantially all of the pressure which holds valve 7l to its seat, is that supplied by spring 08. Thepressure due to this spring, having once been properly determined. can be maintained constant thereafter without being affected by variations in the pressure of the air or other pressure i'luid used to actuate `the motor.

The valve yoke is held in each two extreme positions by spring-actuated toggle links, best shown in Fig. `5. Mounted on the upper face of head t4 with its central portion directly underlying the valve yoke is a plate 93 which projects beyond opposite sides of the valve yoke and has upstanding arms 04 one` on each end thereof. These arms 94 are provided on theirconfronting faces with V-shaped grooves. The valve yoke 8i has in opposite side faces similar grooves. A pair of toggle links 95 are provided, one on each side of the valve yoke, and each interconnects an arm 94 to the yoke. Each toggle link has fixed to its inner end a knife edge 88 which is engaged in a V-shaped groove in the valve yoke. On each link, adjacent the part 96 is a washer 81. A vspring 00 is placed on each link 8E, followed by a washer 90, and a knife edge |00. The upper end of each arm 04 (Fig. 2) has a central notch therein to receive the outer end of thetoggle link and permit it vto slide back and forth relatively thereto. The knife edge |00 (Fig. 5), which is slidable on link 95, nts into the v-shaped groove in an arm 94 and provides a fulcrum for the link. The plate 93 is free to slide, within limits, laterally of the valve yoke 8| in order to equalize the pressure of the springs 08 on the yoke and avoid any side thrust thereon. The head 44 has two upstanding studs IOI which pass through slots bracket to move to the right or left oi' the valve yoke 8| to a suilicient extent to balance the pressure ot the springs 88 on the valve yoke. As a consequence of the arrangement very strong springs may be used. The bottom ot the `valve yoke abuts plate 83 as a stop to limit its down-` ward movement. The yoke has shoulders (Fig. 7), one on each side thereof, to abut the surfaces |08 of the guide 83 as a stop to vlimit the upward movement of the valve yoke. When the yoke is in its lowermost position the valve 'l1 is in its lowermost position and air under pressure will be admitted to the lower end ot cylin-A der 48 and exhausted from its upper end. When the valve yoke is in its uppermost position, the valve 11 is also in its uppermost position and air under pressure will be admitted to the upper end of cylinder 48 and exhausted from the lower end thereof.

-The valve rod 82 (Fig. 3) extends downwardly through head 44 and a suitable sealing device 4#i1 therein and enters a long and axially-directed hole |08 formed in the upper end of the piston rod i0. The power piston comprises a body |08 threaded on the upper end of rod I0 and ilxed in position by a plug I0, forced against rod i0, by a screw |f I, threaded in the opstanding-cylindrical hub portion of body |08. A packing 2, having centrally thereof a stiiening ring |I3, is clamped between the flange portion oi the body |09 and a plate ||4 by a series of cap screws H5,

which pass through the plate and thread into the body |08. The plate ||4 fits over a central hub ||6 on the piston body |09 in order to bring the two packing-compressing lianges into coaxial relation. The valve rod 82 is actuated by the piston near the end of each stroke. To this end, the valve rod carries a snap ring |1 (Fig. 9) set into a circumferential groove in the rod near its lower end. This ring ||1 is a simple and convenient means of providing a flange on the valve rod. Set into a central recess in the upper end oi the hub ||8 and heid in placeby a snap ring ||8 or any other suitable means is a washer ||8 through which rod 82 slides. When the piston moves downwardly, the washer ||8 will, near the end of the plstons stroke, engage ring ||1 and move rod 82 downwardly into the illustrated position. When the piston moves upwardly, the bottom of hole |08 will, near the upper end of the pistons stroke engage the lower end of valve rod 82 and lift it far enough to carry the valve from its lower to its upper position, as will be clear from Fig. 3.

The screws 5|, above described as holding cap 50 in place, thread one into the upper end of a post |20 (Figs. 2 and 5) upstanding from valve seat bracket 55 and the other into the upper end of a similar post |2| upstanding from the guide member 83 for the valve yoke. A

The operation of the motor will next be described. Assuming that the parts occupy the po sitions shown in Fig. 3 and that the supply of compressed air to pipe 33 is turned on, the valve 11 is so positioned as to interconnect the passages 58 and 60. Air under pressure from pipe 33 enters through passage 32', cylinder 3 I, passage 13,

tube 12, passages S4, 81 and 68 (Fig. 4) to passage 58 (Fig. 6) and through valve recess 18 into passage 80 and thence by passages 1|, 10, 86 (Fig. 4), tube 14, and passages 15 and 16 into the lower end of cylinder 48. The piston will thus be moved upwardly. As the piston moves into the interior of cap 50 and thence through I hole 53 (Fig. 2), space 52 (Fig. 3) and slot 84 to the atmosphere. As the piston nears the upper end of its stroke, the bottom wall of hole |08 in piston rod i0 will engagethe bottom of valve rod 82 and lift the latter. The valve yoke 8|- will slide upwardly in its guide 83 without moving valve 11 (Figs. 6 and 7)-the latter being held in position by the pressure applied theretoby the plate 81 and spring 88 (Fig. 6). The inner ends of the toggle links 85 (Fig. 5) will be raised by the yoke 8| until they cross the horizontal plane in which. the fulcrums on arms 84 are located. Then. the springs 88 will expand and force the valve yoke rapidly upwardly, pulling rod 82 upwardly away from vits former actuating member-the bottom of hole |08-and moving valve 11 into its upper position. A rapid and substantially instantaneous reversal of the valve is thus eiected. However, it is important to note that should the toggle springs 88 fail for any reason to move valve 11, the latter will be positively moved, although more slowly, by the motor piston. At the time that the springs 88 are about to move the yoke upwardly the bottom wall of slot (Figs. 5 and '7) will have engaged the lower half of the periphery oi valve 11 and the latter can be moved to its upper position positively by rod 82 and piston rod I0.

The reversal of valve 11 causes the passages 58 and 59 in the valve seat to be connected by the recess 18 in the valve. Accordingly. lair under pressure, entering as before described'into passage 58, passes out through passages 58, 88 and 55 (Fig. 6) into the upperend of cylinder 48. The piston will thus be moved downwardly. The lower endof cylinder 48 is free to exhaust as the piston moved downwardly since the passage 80 is uncovered by valve 11. Air can pass from the lower end of the cylinder (Fig. 4) by way of passages 16 and 15, tube 14, passages 88. 10 and 1|, and slots 88 (Fig. 6) in the valve yoke 8| into the interior of cap 50, whence it escapes to the atmosphere as before described. As the piston nears the lower end of its stroke, the washer ||9 on the piston engages the snap ring on the valve rod 82 and pulls the latter and valve yoke 8| downwardly. The rst result is to swing the inner ends of the toggle links 85 downwardly until they cross the horizontal plane which interconnects the fulcrums on arms 84. Then, the springs 88 expand and rapidly drive the valve yoke downwardly until it abuts plate 83, thereby moving valve 11 substantially instantaneously from its upper to its lower position. I! the springs 98 fail for any reason to thus move the valve, the latter will be positively moved be4 cause the upper wall of slot 80 in the yoke 8| will engagev the upper half of the periphery of the valve 11 and pull it into its lower position.

The reversal of valve 11 will cause air to be admitted to the lower end of cylinder 48 to move the piston upwardly and air to be exhausted from the upper end of the cylinder by upward movement of the piston. The described operation will be repeated as long as the air supply is turned on. If the valve in the grease dispensing nozzle is closed the. air supply is not turned oil, the motor will stall. The valve 38 will not open under such condition but if expansion of the grease should occur as in the hose for example. the valve 38 will open to relieve the excess presd sure and such grease as passes the valve will flow through'passage i2 as a by-pass into the grease drum 3.

The invention provides a generally improved reversing valve mechanism for a fluid-pressureoperated motor oi the reciprocating piston type. A quick, snap action of the valve is secured by relatively simple construction which is calculated to be substantially fool proof in operation and to give a long life of useful service. The valve action is prooi against sprirm failure because it can be moved positively by the valve rod if and when necessary. The valve parts are constructed of materials which are relatively slidable with a low coecient oi friction. The sliding valve is self-lubricating. The air pressure on it is balanced. And the toggle link springs have their pressure on the slidable valve yoke equalized. These factors tend to reduce wear, prolong life and do away with the necessity for frequent servicing. The construction is elcient in operation and also lends itself to manufacture in quantitles at low unit cost.

What I claim is: l

1. A motor comprising, a cylinder including two heads, a shell between the heads and tie bolts for drawing the heads together against the A ends of the shell, said heads having in their confronting iaces a plurality of cylindrical recesses each extending part way into but not through its head, said recesses disposed in pairs with the recesses of each pair disposed on opposite heads and in coaxial relation, tubes one foreach said pair, each tube having its ends'seated' one in each recess oi' a pair, a packingring on each end oi the tube for engaging the peripheral wall of its recess, valve mechanism on one head for controlling the admission and discharge oi pressure fluid to and from each end oi said cylinder, a supply conduit for the pressure uid connected to the other head and communicating with one recess and one end of one tube, the first-named head having a conduit extending from the opposed recess and the other end of the last-named tube to said mechanism and from the latter to a recess and one end ci the other tube, the second-named head having a conduit extending from the opposed recess and the other end of the second-named tube into one end oi said cylinder, the first-named head having a conduit from said mechanism through the head and into the opposite end of the cylinder.

2. A motor, comprising, a base having thereon a cylinder head with inner and outer coaxially-disposed cylindrical surfaces, a second cylinder head having matching inner and outer coaxially-disposed cylindrical surfaces, a cylinder-forming shell having `its ends engaged by the heads and the end portions oi' its periphery engaged with the two inner cylindrical surfaces, tie bolts for drawing the heads together against the ends i the shell, valve mechanism on the 8. n a motor, having a cylinder with heads, a piston in said cylinder, and valve mechanism for controlling the admission of pressure uid to and the discharge of such fluid from the ends A of said cylinder; said mechanism including a slide valve and a valve seat 'therefor fixed to one of l said heads, said seat having a supply portj forl pressure iiuid and two cylinder ports one on each sideof the supply port in the direction of reciprocation of the valve, means operable by the piston to movesaid slide valve first in one and then in an opposite direction from one to the other oi the extremes of its stroke, said valve having a recess in its seat-engaging face to interconnect the supply port first to one and then to the other of the cylinder ports accordingly as it is at one extreme or the other oi its stroke, the valve having in its opposite face an opposed recess of the same congration and area as the rst recess and a passage interconnecting the two recesses, a pressure plate engaging the second` named face of the valve, a spring for pressing the plate against the valve and the latter against its seat, the pressure plate having in the face opposite its valve-engaging face a cylinder having a closed inner end of the same vconfiguration and substantially the same area as each said recess and opposed to such recesses, a xed piston in said cylinder and closing the outer end thereof, said inner end having a passage therethrough, uid pressure from the supply port passing into both recesses and into said cylinder to act equally in opposite directions on the valve and on second head for controlling the admission and the pressure plate, whereby the valve is'y held to said plate solely by the pressure of said spring.

4. lln a motor, having a cylinder with heads, a piston in the cylinder and valve mechanism controlling the admission of pressure fluid to and the discharge of such uid from the cylinder; said mechanism including a cylindrical slide valve reciprocable in the same direction as the piston, a seat for said valve, a reciprocable yoke for moving the valve and having an elongated slot therein with semi-cylindrical ends, said valve being located in said slot and free to rotate, means for moving said yoke by the piston near each end of its stroke, said slot having a dimension in the direction oi reciprocation of the yoke equal to the length of the valve in said direction plus half the stroke of the yoke, and snap-action means conditioned during the rst half of each stroke of the yoke to complete the stroke of the yoke and move the valve from one extreme position to the other.

5. In a motor, having a cylinder with heads land a piston in the cylinder, a valve seat and a plate mounted on one of said heads with their adjacent faces parallel with the axis of the piston, said seat having a supplyport for pressure iluid and two ports connected one to one end and the other to the other end of said cylinder, a slide valve mounted between said seat and plate and reciprocable in the same direction as the piston, yieldable means for maintaining the valve in engagement with the plate and seat, said valve having a recess in one face to interconnect the supply port first to one and then to the other of the cylinder ports and having in the other face a communicating recess of substanyoke, and means movable with the piston for engaging said rod near the end of each stroke and movlns it rst 1n one and then in the op- Number Name Date posits direction to actuate said valve. 2,269,423 Barksv et al. Jan. 13, 1942 WARREN H. DE LANCE'Y. 837,252 nos@ Nov. 27, 1908 l 1,845,176 Palm Feb. 18, 1932 REFERENCES CITED 5 2,257,364 Bystricky 1- Oct. 13, 1936 i 1, 65.921 Joy June 24, 1930 m'h silgvgtge'terenceg are of record n the 2314'714 Kouyoummn Mar. 23 1943 UNITED STATES PATENTS FOREIGN m Number Name Date 10 Number Country vDate 2,163,436 Raymnnd et ax. June 20. 1939 63'691 Sweden Sept' 13 1942 2215 852 mem sept. 24,. 1940 18,865 Great Bumm oct. 189s 

